From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AC55FC4338F for ; Thu, 22 Jul 2021 20:54:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 929BB60EC0 for ; Thu, 22 Jul 2021 20:54:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231516AbhGVUOB (ORCPT ); Thu, 22 Jul 2021 16:14:01 -0400 Received: from mga07.intel.com ([134.134.136.100]:54383 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231313AbhGVUM2 (ORCPT ); Thu, 22 Jul 2021 16:12:28 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10053"; a="275560619" X-IronPort-AV: E=Sophos;i="5.84,262,1620716400"; d="scan'208";a="275560619" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jul 2021 13:53:03 -0700 X-IronPort-AV: E=Sophos;i="5.84,262,1620716400"; d="scan'208";a="502035499" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jul 2021 13:53:02 -0700 From: Yu-cheng Yu To: x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang , Rick P Edgecombe Cc: Yu-cheng Yu Subject: [PATCH v28 23/32] x86/cet/shstk: Add user-mode shadow stack support Date: Thu, 22 Jul 2021 13:52:10 -0700 Message-Id: <20210722205219.7934-24-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20210722205219.7934-1-yu-cheng.yu@intel.com> References: <20210722205219.7934-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Introduce basic shadow stack enabling/disabling/allocation routines. A task's shadow stack is allocated from memory with VM_SHADOW_STACK flag and has a fixed size of min(RLIMIT_STACK, 4GB). Signed-off-by: Yu-cheng Yu Cc: Kees Cook --- v28: - Update shstk_setup() with wrmsrl_safe(). Return success when shadow stack feature is not present, because this is a setup init function and when the feature is not present, no setup is necessary. v27: - Change 'struct cet_status' to 'struct thread_shstk', and change member types from unsigned long to u64. - Re-order local variables in reverse order of length. - WARN_ON_ONCE() when vm_munmap() fails. arch/x86/include/asm/cet.h | 30 +++++++ arch/x86/include/asm/processor.h | 5 ++ arch/x86/kernel/Makefile | 1 + arch/x86/kernel/shstk.c | 134 +++++++++++++++++++++++++++++++ 4 files changed, 170 insertions(+) create mode 100644 arch/x86/include/asm/cet.h create mode 100644 arch/x86/kernel/shstk.c diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h new file mode 100644 index 000000000000..6432baf4de1f --- /dev/null +++ b/arch/x86/include/asm/cet.h @@ -0,0 +1,30 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_CET_H +#define _ASM_X86_CET_H + +#ifndef __ASSEMBLY__ +#include + +struct task_struct; + +/* + * Per-thread CET status + */ +struct thread_shstk { + u64 base; + u64 size; +}; + +#ifdef CONFIG_X86_SHADOW_STACK +int shstk_setup(void); +void shstk_free(struct task_struct *p); +void shstk_disable(void); +#else +static inline int shstk_setup(void) { return 0; } +static inline void shstk_free(struct task_struct *p) {} +static inline void shstk_disable(void) {} +#endif + +#endif /* __ASSEMBLY__ */ + +#endif /* _ASM_X86_CET_H */ diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index f3020c54e2cb..10497634b7a4 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -27,6 +27,7 @@ struct vm86; #include #include #include +#include #include #include @@ -527,6 +528,10 @@ struct thread_struct { */ u32 pkru; +#ifdef CONFIG_X86_SHADOW_STACK + struct thread_shstk shstk; +#endif + /* Floating point and extended processor state */ struct fpu fpu; /* diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 3e625c61f008..9e064845e497 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -150,6 +150,7 @@ obj-$(CONFIG_UNWINDER_FRAME_POINTER) += unwind_frame.o obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o obj-$(CONFIG_AMD_MEM_ENCRYPT) += sev.o +obj-$(CONFIG_X86_SHADOW_STACK) += shstk.o ### # 64 bit specific files ifeq ($(CONFIG_X86_64),y) diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c new file mode 100644 index 000000000000..5993aa8db338 --- /dev/null +++ b/arch/x86/kernel/shstk.c @@ -0,0 +1,134 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * shstk.c - Intel shadow stack support + * + * Copyright (c) 2021, Intel Corporation. + * Yu-cheng Yu + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +static void start_update_msrs(void) +{ + fpregs_lock(); + if (test_thread_flag(TIF_NEED_FPU_LOAD)) + fpregs_restore_userregs(); +} + +static void end_update_msrs(void) +{ + fpregs_unlock(); +} + +static unsigned long alloc_shstk(unsigned long size) +{ + int flags = MAP_ANONYMOUS | MAP_PRIVATE; + struct mm_struct *mm = current->mm; + unsigned long addr, populate; + + mmap_write_lock(mm); + addr = do_mmap(NULL, 0, size, PROT_READ, flags, VM_SHADOW_STACK, 0, + &populate, NULL); + mmap_write_unlock(mm); + + return addr; +} + +int shstk_setup(void) +{ + struct thread_shstk *shstk = ¤t->thread.shstk; + unsigned long addr, size; + int err; + + if (!cpu_feature_enabled(X86_FEATURE_SHSTK)) + return 0; + + size = round_up(min_t(unsigned long long, rlimit(RLIMIT_STACK), SZ_4G), PAGE_SIZE); + addr = alloc_shstk(size); + if (IS_ERR_VALUE(addr)) + return PTR_ERR((void *)addr); + + start_update_msrs(); + err = wrmsrl_safe(MSR_IA32_PL3_SSP, addr + size); + if (!err) + wrmsrl_safe(MSR_IA32_U_CET, CET_SHSTK_EN); + end_update_msrs(); + + if (!err) { + shstk->base = addr; + shstk->size = size; + } + + return err; +} + +void shstk_free(struct task_struct *tsk) +{ + struct thread_shstk *shstk = &tsk->thread.shstk; + + if (!cpu_feature_enabled(X86_FEATURE_SHSTK) || + !shstk->size || + !shstk->base) + return; + + if (!tsk->mm) + return; + + while (1) { + int r; + + r = vm_munmap(shstk->base, shstk->size); + + /* + * vm_munmap() returns -EINTR when mmap_lock is held by + * something else, and that lock should not be held for a + * long time. Retry it for the case. + */ + if (r == -EINTR) { + cond_resched(); + continue; + } + + /* + * For all other types of vm_munmap() failure, either the + * system is out of memory or there is bug. + */ + WARN_ON_ONCE(r); + break; + } + + shstk->base = 0; + shstk->size = 0; +} + +void shstk_disable(void) +{ + struct thread_shstk *shstk = ¤t->thread.shstk; + u64 msr_val; + + if (!cpu_feature_enabled(X86_FEATURE_SHSTK) || + !shstk->size || + !shstk->base) + return; + + start_update_msrs(); + rdmsrl(MSR_IA32_U_CET, msr_val); + wrmsrl(MSR_IA32_U_CET, msr_val & ~CET_SHSTK_EN); + wrmsrl(MSR_IA32_PL3_SSP, 0); + end_update_msrs(); + + shstk_free(current); +} -- 2.21.0